Single well secondary recovery process



March 9, 1965 J. l.. Hun-T ETAL 3,172,470

SINGLE wELL SECONDARY RECOVERY PRocEss med Nov. 2,1. 19Go @fw/wak ATTRNEY United States Patent O f 3,172,470 SINGLE WELL SECONDARY RECVERY PRCESS Jimmie L. Hutt, Glenshaw, and .lohn Papaila, Apollo, Pa., assignors to Gulf Research & Development Conrpany, Pittsburgh, Pan, a corporation of Delaware Filed Nov. 21, 196i), Ser. No. 70,732 9 Claims. (Cl. 166-29) This invention relates to the production of oil from oilbearing formations and more particularly to a secondary recovery process for the production of oil.

Frequently an oil reservoir will not be under sufficient pressure to move the oil through the formation to the borehole of a well at a fast enough rate to allow commercial production of a Well. Secondary recovery processes in which a gas, or a liquid such as water, is injected into an' oil reservoir to supply the energy for moving the oil to the well are widely used to increase the amount of oil recovered from the reservoir. In the usual secondary recovery process a uid is injected into the reservoir at one well, usually called an injection well, to drive oil through the reservoir to a second well, ordinarily referred to as a production Well, spaced from the injection well.

In some instances it is desirable to use a single well for both the injection of the driving lluid and the production of oil in a secondary recovery process. For example, it has been suggested that a gas be delivered through the annulus of a well into the upper portion of the pay Zone and oil be withdrawn from the bottom of the pay zone into the well. When a driving liuid is injected into an oilbearing formation at high rates to increase the rate of production from the well there is a tendency for the injected fluid to bypass much of the oil in the formation and flow immediately adjacent the borehole o-f the well to the area at which production enters the well.

This invention resides in a secondary recovery process for the recovery of oil from a formation utilizing a single well in which a substantially horizontal fracture is made in an oil-bearing formation and the faces of the fracture sealed while the fracture is maintained open. After the faces of the fracture have been sealed, the fracture is extended radially and a driving fluid displaced through the fracture outwardly through the extension of the fracture into the formation to drive oil from the forrnat tion into the well through which the oil is lifted to the surface. The process of this invention is suitable for use in an in situ combustion process as well as in gas,

micible fluid, or water drive secondary recovery processes. V The single figure of the drawing is a diagrammatic-` Referring to the drawing, a well indicated generally I by reference numeral 1t? is illustrated extending down-l wardly through an oil-bearing formation 12 to a total depth 14. The well is provided with casing 16 cemented in place completely through the oilbearing formation 12 in accordance with conventional practice to form a cement sheath 18 surrounding the casing. paratus illustrated in the drawing, casing 16 is provided with a side outlet 2i) above the surface 22 of the ground. The upper end of the casing 16 is closed by suitable means such as a cap 24.

Perforations 26 are made in casing 16 at intervals in the upper portion of the pay Zone 12. The perforations 26 may be made by any of the usual means such as bullets, shaped explosive charges, and abrasive jets, commonly used for that purpose. After the perforations 26 have been made a horizontal ring is cut from In the ap-` 3,172,476 Patented Mar. 9, 1965 ICC the casing 16 at 23, below the perforations 26 and above the lower boundary 30 of the oil-bearing formation 12, by suitable means such as a mechanical milling tool or an abrasive slurry. After removal of the ring of the casing a notch is cut through the cement sheath 18 surrounding the casing and into the underground formation at the level of the ring 28 cut from the casing.

A packer 32 is set in the casing 16 between the perforations 26 and the cut made in the casing at 28. The packer 32 may be run and set in place 4on tubing 34 which extends through the packer and opens below the packer into the casing 16. The setting of the packer 32 and running of the tubing can be performed in any conventional manner and the packer 32 may be first set in the casing and the tubing 34 then run into the Well and through the packer.

A horizontal fracture 36 is then formed as an extension of the notch cut in the oil-bearing formation by, for example, a suitable modification of the method described in U.S. Patent No. 2,699,212 for the formation of a vertical fracture. The fracture is formed by displacing a suitable liquid down through tubing 34 at a pressure high enough to overcome the overburden pressure and the strength of the formation rock. Water or lease crude oil are commonly used in forming a fracture from an oil well. In some instances, it may be desirable to add synthetic or natural gums or polymers, soaps, or gelling agents to the fracturing liquid to increase the resistance of flow of the liquid into the formation. Such viscosity-increasing materials can subsequently be removed or destroyed in accordance with the usual procedures by flushing or by the introduction of a material adapted to reduce the viscosity of the fracturing liquid.

Fracture 36 is extended radially into the formation for a distance depending upon the characteristics of the reservoir. Fractures extending four hundred feet or more radially from the well bore can be made and are preferred because of the large area swept by the subsequent lluid drive. After the fracture 36 has been made of the desired radius, a sealing material is displaced into the fracture and pressure applied to the sealing material by a liquid under a pressure controlled to displace the sealing material from the fracture into the formation above and below the fracture rather than to extend the fracture radially.

A wide variety of sealing materials are suitable for use in this invention. For example, the sealing material may be merely a finely powdered solid material such as silica powder or finely divided clays which damage the walls of the fracture to greatly retard subsequent flow of iiuids through those walls. A number of organic cornpounds which will polymerize or condense to form solid resinous material, insoluble in oil and water, also can be used. Typical suitable materials are synthetic resinforming materials such as phenol-formaldehyde compositions and urea-formaldehyde compositions, or monomers of acrylonitrile or butadiene. A large number of such natural or synthetic materials have been suggested for displacement into the formations to seal the formations to prevent the influx of water. The displacement of a resin-forming liquid into an underground formation to destroy its permeability is described in Patent No. 2,274,297 of Irons. Another suitable sealing `material is a high melting point asphalt which may be heated to a temperature at which it is fluid and displaced from the fracture into the formation forming the upper and lower faces of the fracture.

Another method of sealing the faces of the fracture is to displace an aqueous solution of a salt from the fracture into the formation above and below the fracture and follow the solution with a gaseous material which penetrates the formation and reacts with the aqueousv solution to form a precipitate for a substantial depth into the formation. An aqueous solution of aluminum sulfate followed by gaseous ammonia, which may be mixed with an inert gas such as nitrogen or methane to prevent condensation of the ammonia, is suitable'for this purpose. Still another method which is particularly suitable when an aqueous fracturing fluid has been used is to inject silicon tetrafluoride into the fracture. Silicon tetrailuoride hydrolyzes upon Contact with water and forms a solid siliceous deposit which effectively plugs the formation. Y

After injection of the sealing material into the formation a propping agent suspended in a liquid is pumped down the well and displaced into the fracture. The liquid used as a medium for carrying the propping agent into the fracture flushes sealing composition from the fracture into the formation and thereby insures the fracture being maintained open. The well is thenshut in for a period sufficient for the sealing material to set to form the desired seal preventing flow into the fracture.

Following the setting of the sealing composition, a fluid, preferably a low fluid loss liquid, is pumped down through tubing 34 and displaced into the fracture. The pressure applied to the fluid'is increased and the pumping of the fluid into the fracture is continued at a rate to form an extension 38 of the fracture radially beyond the plugged walls of fracture 36. Preferably, a propping agent, indicated by reference numeral 40, is added to liquid pumped into the extension 33 after the extension has been formed to prop the extension open.

Gil is'produced from the well 10 by displacing water downwardly through tubing 3d into fracture 36. The sealed walls of the fracture 36`prevent the water from entering the oil-bearing formation except at 'the extensions 38 of the fracture. The water then flows radially inward from the extensions 38 of the fracture toward the well and drives oil in the formation into the annular space surroundingtubing 34 through the perforations `2.6. assumed. that the pressure applied to formation 12 is adequate to lift the oil through thek annulus to the surface for` discharge "through outletzt) to simplify the apparatus shown in the drawing. If desired, suitable lifting apparatus such as a pump may be installed forlifting the fluid delivered into the well 10 through perforations 26 to the surface.

In a specific example of this invention, oil is to be recovered through a well penetrating a small lenticular oil reservoir at a depth between 1883 and 1903 feet. The well is prepared for fracturing by cutting a notch in the borehole wall of the well at 1902 feet. The formation is broken down and fractured in the conventional manner with 50,000 gallons of gelled water containing 0.2 pound per gallon of silica powder, followed by 60,000 gallons of gelled water containing one pound Yper gallon of 6-8 mesh sand. The well is shut in for 48 hours and the casing is then perforated in the 18834893 foot interval. An injection string of tubing is run and a packer on the injection string is set at 1895 feet. Flood water is injected through the injection tubing and oil is produced through the annulusk of the secondary recovery operation.

This invention is suitable for the production of oil by gas or water drive, or by in situ combustion. The sealing material selected to seal the faces of the fracture will depend upon the type of secondary recovery process that is to be used and shouldbecapable of withstanding the fluid and conditions existingrin the process. For example, a water-insoluble sealing material should be used in a water flood process and a sealing material capable of withstanding high temperatures should be used in an in situ combustion process. If the process is to be used forin situ combustion the oil in the formation In the well illustrated in the drawing, it is L" at the extremities of the fracture can be ignited by displacing a solution of phosphorus and carbon disulfide through the fracture and into the formation surrounding the extension 38. After the solution of/phosphorus is displaced into the formation air is displaced through the fracture into the formation. The air upon contact with the phosphorus ignites the phosphorus to supply 'the heat required for ignition of oil -in the oil-bearing formation 12.

The location of the fracture is dependent upon the reservoir characteristics and the type of secondary recovery process employed. Fracture 36 may be made at any point inthe oil-bearing formation l2. In some instancesV it may be desirable to form the fracture near the top of the oil-bearing formation and inject gas to drive formation fluids through perforations in the casing at theplower part of the oil-bearing formation. In another arrangement the fracture can be made near the lower boundary of the reservoir and water injected through the fracture to drive oil in the formation through perforations above the fracture. The fracture 36 also may be made at substantially the Vmiddle of the formation with perforations both above andk below the fracture to allow oil to flow 'through the formation both above and below the fracture into the well. Such an arrangement will necessitate a more complicated arrangement within the borehole for delivery of oil to the surface.

The process of this invention reduces the short circuiting of oil in the pay zone by -a fluid injected into the pay zone in a single well secondary recovery process. This invention is particularly suited for use in thin pay zones in that it allows an efficient sweep'pattern to be obtained with a single fracture employed for construction of a barrier to prevent bypassing of the formation as well as delivery of fluids. intothe formation.

We claim:

1. A method for the production of oil from an oilbearing formation penetrated by the borehole of a Well comprising forming a substantially horizontal fracture extending from the borehole of the well into the oilbearing formation, setting a packer in the borehole adjacent the fracture to divide the borehole into a first section communicating with the fracture and a second section communicating with the pay zone at a depth different than the depth of the fracture, running tubing down the well and through the packer to provide a conduit from the wellhead to the borehole below the packer, injecting a sealing material into the fracture and from the fracture into the formation adjacent the walls thereof to substantially permanently plug the walls of the fracture substantially continuously from the borehole to the outer extremity of the fracture to prevent flow of fluids between the formation and the fracture, thereafter pumping `a fluid free of sealing material into the fracture under a pressure adapt-ed to form an extension of the fracture radially beyond the plugged formation, injecting a fluid down the first section of the well and outwardly through the fracture and extension of the fracture into the formation adjacent said extension to drive oil through the oil-bearing formation to the second section of the borehole of the well, and lifting oil through said second section of the well.

2. A method as set forth in claim 1 in which the walls of the fracture are plugged with a water-insoluble material, and the fluid injected down the first section of the well outwardly through .the fracture and extension of the fracture is water.

3. A method as set forth in claim 1 in which the formation walls of the fracture are plugged with a material insoluble in hydrocarbons, and the fluid injected down the first section of the well and outwardlythrough the fracture and extension of the fracture includes hydrocarbons.

4. A method as set forth in claim 1 in which .the walls of the fracture are plugged with a heat resistant material, and the lluid injected down the first section of the well and outwardly through the fracturey and extension of the frac* ture is an oxygen-containing gas adapted to support combustion of oil in the oil-bearing formation.

5. A method as set forth in claim 1 in which the sealing material is finely powdered silica.

6. A method for the production of oil from an oilbearing formation penetrated by the boreh-ole of a well comprising forming a substantially horizontal fracture extending from the Iborehole of the well into the oil-bearing formation, isolating the fracture from at least a portion of the borehole in the interval of the oil-bearing formation, injecting a sealing material down the well and into the fracture and from the fracture into the walls of the fracture, injecting a liquid devoid of sealing material down the well and into the fracture to displace the sealing material from the fracture into the Walls of the fracture, shutting the well in to set the sealing material while maintaining the fracture open whereby the walls of the fracture are substantially permanently plugged substantially continuously from the borehole wall to the outer extremity of the fracture to prevent fluid flow through said walls, thereafter injecting a liquid down the well and into the fracture and applying pressure thereto to extend 4the fracture radially beyond the plugged walls of the fracture, setting a packer in the well adjacent the fracture to divide the well into a first section communicating with the fracture and a second section communicating with the oil-bearing formation at `a point spaced from the fracture, running tubing down the well and through the packer to provide a conduit from the well head to the borehole below the packer, injecting a fluid down the first section of the well and outwardly through the fracture and extension thereof into the oil-bearing formation to drive oil inwardly toward the second section of the well, and producing oil through the second section of the well.

7. A method for the production of oil from an oilbearing formation penetrated by the borehole of a well comprising forming a substantially horizontal fracture extending from the borehole of the well into the oil-bearing formation, isolating the fracture from at least a portion of the borehole through the interval of the oil-bearing formation, injecting a sealing material down the well and into the fracture and from the fracture into the walls of the fracture, injecting a liquid devoid of sealing material down the well and into the fracture to displace the sealing material from the fracture into the walls of the fracture, shutting the well in to set the sealing material whereby the walls of the fracture are substantially permanently plugged substantially continuously from the borehole to the outer extremity of the fracture to prevent uid flow through said walls, thereafter injecting a liquid down the well and applying pressure thereto to extend the fracture radially beyond the plugged walls of the fracture, depositing a propping agent in the fracture and extension, setting a packer in the well adjacent the fracture to divide the well into a first section communicating with the fracture and a second section communicating with the oil-bearing formation at `a point spaced from the fracture, running tubing down the well and through the packer to provide a conduit from the well head to the borehole below the packer, injecting a fluid down the first section of the well and outwardly through the fracture to the extension thereof and into the oil-bearing formation to drive oil inwardly toward the second section of Ithe well, and producing oil through the second section of the well.

8. A method for the production of oil from an oilbearing formation penetrated by the borehole of a well comprising forming a substantially horizontal fracture extending radially outwardly frorn the borehole of the well into the oil-bearing formation, isolating the fracture from at least a portion of the borehole through the interval of the oil-bearing formation, injecting a heat resistant sealing mater-ial into the fracture and from the fracture into the Walls of the fracture to substantially permanently plug said walls substantially continuously from the borehole to the outer end of the fracture and prevent ow of fluids through said walls, thereafter forming an extension of the fracture radially beyond the plugged formation, depositing a p-ropping agent in the fracture and extension to maintain the fracture open, injecting a pyrophoric material down the borehole and outwardly through the fracture into the formation adjacent the exten-sion of the fracture, setting a packer in the borehole of the well adjacent the fracture to divide the well into a first section communicating with the fracture and a second section communicating with the oil-bearing formation at a point spaced from the fracture, running tubing through the packer t-o provide a conduit from the wellhead to the borehole below the packer, injecting an oxygen-containing gas through the first section of the well and outwardly through the fracture into the formation adjacent the extension of the fracture to initiate combustion of oil in the formation, and producing oil through the second section of the well.

9. A method for the pro-duction of oil from an oilbearing formation penetrated by the borehole of a well comprising forming a substantially horizontal fracture extending radially outwardly from the borehole of the well into the oil-bearing formation, isolating the fracture from at least a portion of the borehole through the interval of the oil-bearing formation, injecting a heat resistant sealing material into the fracture and from the fracture into the walls of the fracture to substantially permanently plug said walls substantially continuously from the borehole to the outer end of the fracture and prevent flow of fluids through said walls, thereafter forming an extension of the fracture radially beyond the plugged formation, depositing a propping agent in the fracture and extension to maintain the fracture open, setting a packer in the borehole of the well adjacent the fracture to divide the well into a first section communicating with the fracture and a second section communicating with the oil-bearing formation at a point spaced from the fracture, running tubing through the packer to provide a conduit from the wellhead to the borehole below the packer, injecting an oxygen-containing gas through the rst section of the well and outwardly through the fracture into the formation adjacent the extension of the fracture, igniting oil in the formation, continuing the injection of the oxygen-containing gas to cause insitu combustion of oil in the formation, and producing oil through the second section of the well.

References Cited in the le of this patent UNITED STATES PATENTS 2,699,212 Dismukes Ian. 11, 1955 2,805,721 Maly Sept. 10, 1957 2,821,255 Spearow Ian. 28, 1958 2,862,556 Tek Dec. 2, 1958 2,874,777 Tadema Feb. 24, 1959 2,896,717 Howard July 28, 1959 2,959,223 Harmon et al Nov. 8, 1960 

1. A METHOD FOR THE PRODUCTION OF OIL FROM AN OILBEARING FORMATION PENETRATED BY THE BOREHOLE OF A WELL COMPRISING FORMING A SUBSTANTIALLY HORIZONTAL FRACTURE EXTENDING FROM THE BOREHOLE OF THE WELL INTO THE OILBEARING FORMATION, SETTING A PACKET IN THE BOREHOLE ADJACENT THE STRUCTURE TO DIVIDE THE BOREHOLE INTO A FIRST SECTION COMMUNICATING WITH THE FRACTURE AND A SECOND SECTION COMMUNICATING WITH THE PAY ZONE AT A DEPTH DIFFERENT THAN THE DEPTH OF THE FRACTURE, RUNNING TUBING DOWN THE WELL AND THROUGH THE PACKER TO PROVIDE A CONDUIT FROM THE WELL HEAD TO THE BOREHOLE BELOW THE PACKER, INJECTING A SEALING MATERIAL INTO THE FRACTURE AND FROM THE FRACTURE INTO THE FORMATION ADJACENT THE WALLS THEREOF TO SUBSTANTIALLY PERMANENTLY PLUG THE WALLS OF THE FRACTURE SUBSTANTIALLY CONTINUOUSLY FROM THE BOREHOLE TO THE OUTER EXTREMITY OF THE FRACTURE TO PREVENT FLOW OF FLUIDS BETWEEN THE FORMATION AND THE FRACTURE, THEREAFTER PUMPING A FLUID FREE OF SEALING MATERIAL INTO THE FRACTURE UNDER A PRESSURE ADAPTED TO FORM AN EXTENSION OF THE FRACTURE RADIALLY BEYOND THE PLUGGED FORMATION, INJECTING A FLUID DOWN THE FIRST SECTION OF THE WELL AND OUTWARDLY THROUGH THE FRACTURE AND EXTENSION OF 